sane-find-scanner:
# sane-find-scanner will now attempt to detect your scanner. If the
# result is different from what you expected, first make sure your
# scanner is powered up and properly connected to your computer.

# No SCSI scanners found. If you expected something different, make sure that
# you have loaded a kernel SCSI driver for your SCSI adapter.

found USB scanner (vendor=0x04f9, product=0x01a8) at libusb:003:002
# Your USB scanner was (probably) detected. It may or may not be supported by
# SANE. Try scanimage -L and read the backend's manpage.

# Not checking for parallel port scanners.

# Most Scanners connected to the parallel port or other proprietary ports
# can't be detected by this program.

# You may want to run this program as root to find all devices. Once you
# found the scanner devices, be sure to adjust access permissions as
# necessary.

sudo sane-find-scanner:
# sane-find-scanner will now attempt to detect your scanner. If the
# result is different from what you expected, first make sure your
# scanner is powered up and properly connected to your computer.

# No SCSI scanners found. If you expected something different, make sure that
# you have loaded a kernel SCSI driver for your SCSI adapter.

found USB scanner (vendor=0x04f9, product=0x01a8) at libusb:003:002
# Your USB scanner was (probably) detected. It may or may not be supported by
# SANE. Try scanimage -L and read the backend's manpage.

# Not checking for parallel port scanners.

# Most Scanners connected to the parallel port or other proprietary ports
# can't be detected by this program.

Probably the same problem as bug #121082 -- the udev scanner rules have been removed and whatever hal is supposed to be doing instead isn't working. Try getting a copy of /etc/udev/rules.d/45-libsane.rules from a gutsy machine (and I'll attach a copy here) -- that fixed it here.

I am using 8.10 and it is not working.
The workaround by Brother didn't help, because the suggested changes were already done.
That is what it looked like right from the start.
# USB devices (usbfs replacement)
SUBSYSTEM=="usb", ENV{DEVTYPE}=="usb_device", MODE="0666"
SUBSYSTEM=="usb_device", MODE="0666"
Also see my comments here: https://bugs.launchpad.net/ubuntu/+bug/324783
I am going to contact their support and maybe we can get something out of it :)

[...] Packages do not generally install rules here, this directory is for
local rules. If you want to override behaviour of package-supplied
rules, which can be found in /lib/udev/rules.d, you can do one of
two things:

1) Write your own rules in this directory that assign the name,
symlinks, permissions, etc. that you want. Pick a number higher
than the rules you want to override, and yours will be used.

2) Copy the file from /lib/udev/rules.d and edit it here; you
should generally only do this if you want to prevent a program
from being run.
[...]

I didn't have much time to experiment with a local rules files, so I went ahead and edited directly this file:
/lib/udev/rules.d/50-udev-default.rules

And it worked for me. So my workaround for this problem is:
1) Open a terminal window
2) gksudo gedit /lib/udev/rules.d/50-udev-default.rules
3) Make sure the following line has MODE=" 0666" at the end:

[Solved for Jaunty]
My solution to only being able to use a scanner as root in Jaunty, much simpler than udev.rules, is:
1) lsusb
.......
Bus 002 Device 002: ID 04f9:0182 Brother Industries, Ltd Composite Device

(but see also sudo xsane , where the xsane top panel says 0.996 DCP-7010:bus3;dev2 )

2) sudo pcmanfm
go to /dev/bus/usb/002/002
(Might want to try /dev/bus/usb/003/002 as well if this bus no. confusion exists)
Right mouse click > properties > permissions
Allow Run for Group and Other Users.

Your solution works of course, but it is manual work and we want to
avoid setting permissions manually to invidivual devices. Therefore the
correct solution would be to fix udev rules so that the device's
permissions are correct by default.

I hope somebody with access to the upstream udev rules would fix this
now, please.

The VPablos fix doesn't work for me on Ubuntu Jaunty 9.04, because it disables both of my USB mice multiseat setup. What I had to do for my Fujitsu 4120c is to add file
/etc/udev/rules.d/45-libsane.rules
with the following content

I too have a networked Brother MFC-7440N with the same problem.. nothing Brother suggested worked.. their last suggestion was to reinstall my os. Works with sudo xsane, doesn't work with standard user.. Ubuntu 8.10 & 8.04 (two different machines.

While the minmal-invasive solution for just a single device does not work, the solution provided by VPablo works in 9.10 as well. Since there does not seem to be a default rules file anymore, I added the file /etc/udev/rules.d/95-udev-late.rules, having the following content:

Brother has new instructions and a .deb for Ubuntu. It's not the easiest thing to wade through their instructions to piece everything together for a distro and for each function. I recently did a fresh install of Kubuntu 9.10 and installed the driver(s). So far printing and scanning work like a charm. I've yet to get the faxing to work. I've attached step by step instructions as to what I did to get things working.. This should work the same on ubuntu as it does on kubuntu. I should note that in Brothers instructions there is mention that Ubuntu releases prior to (one I forgot) need to follow the instructions differently.

Same problem here with xubuntu 9.10 and a Mustek 600 II N scanner. I'm able to scan when doing a sudo xsane but not as normal user. Creating such a rules file (as mentioned in former posts) is not an option for me because the scanner is not a USB scanner (it has on own ISA card which seems to be a kind of parallel port - the scanner is also powered by this card). At least I don't have an idea which kind of port numbers or vendor numbers I need to add.

creating /lib/udev/rules.d/50-scanner.rules with the line: ATTRS{idVendor}=="05da", ATTRS{idProduct}=="00b6", MODE="664",GROUP="scanner" and creating the group "scanner" and adding myself to that group fixed it.